The objective of the present study is to compare the associated costs of long-term storage of spent nuclear fuel—open cycle strategy—with the associated cost of reprocessing and recycling strategy of spent fuel—closed cycle strategy—based on the current international studies. The analysis presents cost trends for both strategies. Also, to point out the fact that the total cost of spent nuclear fuel management (open cycle) is impossible to establish at present, while the related costs of the closed cycle are stable and known, averting uncertainties.
The current demand of resources and the increasing and intensive energy consumption per capita have motivated development policies of efficient forms of energy in the electric generation area. Nuclear and renewable energies play an important role in our energy future, helping to meet increasing electricity demand while at the same time decreasing carbon dioxide emissions [
Over the last decade, numerous assessments [
Högselius [
The UK’s nuclear energy landscape assessment [
Studies developed in US will need to compare each of the fuel cycle options regarding sustainability, proliferation risk, commercial viability, waste management, and energy security in order to define the future of nuclear power [
Although China’s nuclear power industry is relatively young and the management of its spent nuclear fuel is not yet a concern, China’s commitment to nuclear energy and its rapid pace of development require detailed analyses of its future spent fuel management policies. Zhou [
Suchitra [
The purpose of this report is to analyze and compare the results obtained from studies conducted by the Nuclear Energy Agency (NEA) for the Organization for Economic Co-operation and Development (OECD) in 1985 [
Currently, the production of electricity from nuclear sources is based on the “fission” of U235 and, in lesser proportions, Pu239. In order to better understand this process, we will review some of the concepts and milestones regarding this technology, albeit in a very simplified manner, as this paper focuses on economic aspects of management.
In light water reactor nuclear power plants such as those found in Western countries, fission is produced in the previously mentioned atoms. This fission generates energy which is then used to heat water from a cooling cycle which evaporates and enters into a steam generator, thereby producing electricity. With this “nuclear fuel fission” reaction, new isotopes, products of the fission, are created in the nuclear reactor. At the same time, transuranic elements are transmuted by neutron capture into actinides which are capable of fission and energy generation.
As the U-235 nuclei continue the fission process, the amount of fissile material decreases while the fission and actinide products increase until reaching the point in which the chain reaction is no longer maintained in the reactor. To prevent this, fuel elements must be substituted for the other nonirradiated elements.
The used fuel found in the light water reactors consists of uranium oxide enriched in isotope 235 by a variable percentage of approximately 5%. As previously indicated, some reactors use a mixture of enriched uranium and Pu-239, which is produced in the reactor. Natural uranium, which is extracted from mines, only contains roughly 0.7% of U-235. The natural uranium is concentrated and converted into uranium hexafluoride. This compound is enriched by the necessary quantity of U-235 in order to reach the required percentage for the reactor.
After its use in the reactor, the fuel is then discharged. The exact composition of the used fuel depends on the amount of time it was in the reactor as well as on the neutron flux levels to which it was subjected. In schematic terms, nuclear fuel evolution can be represented as shown in Figure
Evolution of fuel from a nuclear reactor during an operating cycle.
The evolution of fuel during irradiation in a reactor can be simplified in the following manner. The content of U-235, initially at 4%, is reduced to 1%. The 3% of U-235 is converted into fission products (FP). The 3% of U-238 is converted principally into Pu and, in lesser amounts, into other transuranic elements, minor actinides (MA). A portion of the Pu has fissioned, increasing the quantity of fission products.
When the fuel elements are removed from the reactor, they are deposited into specially prepared pools which are located in the nuclear plant complex in order to release any residual thermal energy and to reduce their level of radioactivity for later treatment, be it in the final waste deposit site or in reprocessing for subsequent recycling.
For very long-term management of these elements, transmutation or fission technologies in accelerator-assisted systems or Generation IV fast reactors are considered. In this way, the radiotoxicity of the radioactive waste, in a period of one-hundred years, will be reduced to levels existing naturally, due to the naturally radioactive elements of which they are composed.
These technologies are still in a developmental phase and have yet to be applied to an industrial scale. As previously mentioned, there are two existing alternatives for the definitive management of used fuel elements in a final stage. The elements can be safely stored in stable deep geological repositories (
Two countries, Sweden and Finland, have definitively adopted the open cycle and are in the preconstruction phase of the geological repositories for fuel element storage in copper capsules with granite subsoil.
One of the principles of any waste management policy in developed countries is that of reducing, recycling, and reusing waste products. The application of this principle to radioactive waste requires separating the unused and/or produced fissile material, reusing the material in new fuels, as previously described, and reducing the highly active waste to minor actinides—fission products that are obtained in a reactor by uranium transmutation.
In the closed cycle option, as it is currently practiced, after cooling the used fuel through chemical and mechanical processes, the recyclable uranium and plutonium materials are separated, so as to be used in the fabrication of new ERU fuels, and MOX fuels (Mixed Oxides with uranium and plutonium), which can be used in conventional reactors. This recycled fuel offers savings of up to 25% in natural uranium [
Those countries with reprocessing facilities are France, Russia, the United Kingdom, Japan, India, Pakistan, and, most recently, China. However, many other countries reprocess or have reprocessed part of their used fuel, although they do not have their own facilities, and they recycle or have recycled in their reactors. This is the case in Holland, a country which has reprocessed the total amount of its used fuel and has a centralized storage facility where they store reprocessed vitrified waste instead of used fuel.
Today, some 90,000 tons of used fuels (of the 290,000 tons discharged) from commercial reactors have been reprocessed [
It is noteworthy to mention that the large majority of countries [
In Spain, some 2,000 tons of low- and medium-activity waste are produced annually along with some 160 tons of high activity waste. The eight operating nuclear reactors in Spain produced 21% of the electric energy that was consumed in Spain in 2011 and generated 95% of this waste.
The absence of a definitive decision regarding the final destination of the used fuel and the delay in the creation of programs for deep geological repositories (DGR) have created the need for temporary solutions: increased capacities of the used fuel pools in the plants, construction of temporary storage sites near the plants, and, key for Spanish used-fuel management: a project to create a temporary centralized storage facility.
On December 30, 2011, the Spanish Council of Ministers approved a resolution whereby the municipality of Villar de Cañas (Castilla-La Mancha) was chosen as site of the temporary centralized storage facility for highly active nuclear waste and used fuel generated by the Spanish nuclear energy industry. Planned for a total period of sixty years, this site will store all of the used fuel generated in the eight reactors in Spain for forty years—some 6,700 tons of used fuel.
The methodology followed to evaluate the values presented in the analyzed reports consists of the comparison of three concepts: the cost of uranium ore, the storage costs in deep geological repositories (DGR), and the cost of reprocessing the spent nuclear fuel. In order to work with comparable values, the criteria used for each cost has been as follows. Cost of uranium ore: over the past years, the uranium price has shown an increasing trend of $36/lb. U3O8 reaching a maximum of almost $45/lb U3O8 in 1975–1980, and a second maximum of $136/lb U3O8 in 2007. This trend is shown in Figure DGR cost: the storage cost for spent nuclear fuel has been considered to be the cost per kilogram of heavy metal (kg HM) stored. Transport costs, combustible costs for transport, encapsulating costs, and uranium credits are not included. Reprocessing cost: the cost of reprocessing the spent nuclear fuel includes reprocessing costs per se and the cost of vitrification.
Uranium price chart.
In each study, a sensitivity analysis was carried out for the different variables, with the DGR costs as well as the reprocessing costs having nominal values within a range with upper and lower margins. The criterion used to determine the nominal value is described in detail in each report.
Table
Results from the studies.
NEA-OECD (1985) [ |
NEA-OECD (1991) [ |
MIT (2003) [ |
BCG (2006) [ |
EPRI (2010) [ |
De Roo and Parsons (2011) [ | |
---|---|---|---|---|---|---|
Uranium price |
83.2 | 50 | 30 | 68.8 | 260 | 80 |
DGR cost |
150 | 190 | 400 | 320 | 354 | 470 |
Reprocessing cost |
790 | 770 | 1100 | 725 | 1100 | 1600 |
In order to make an appropriate cost comparison, the prices have been updated to the year 2011 using the following conversion equation:
with
Table
Results obtained from studies updated to 2011.
NEA-OECD (1985) [ |
NEA-OECD (1991) [ |
MIT (2003) [ |
BCG (2006) [ |
EPRI (2010) [ |
De Roo and Parsons (2011) [ | |
---|---|---|---|---|---|---|
Uranium price |
149.8 | 81 | 43.7 | 80.6 | 276.5 | 89 |
DGR cost |
270.1 | 308.1 | 582.8 | 375.2 | 376.5 | 422 |
Reprocessing cost |
1422.4 | 1248.3 | 1458 | 1602.6 | 1783.6 | 1169.7 |
In order to analyze the values updated to the year 2011 for each report, a graphic evaluation of the DGR costs versus time has been created as shown in Figure
DGR costs trend.
The differences between the DGP costs trend published by the OCDE and BCG (growing trend) and the MIT and De Roo (decreasing trend) are remarkable. As stated in an OCDE study dedicated to geologic disposal, 1993, “Permanent geologic disposal of spent fuel and HLW has not been demonstrated, and approaches to waste disposal vary considerably from country to country, making cost estimates highly uncertain” [
A second analysis carried out to compare the trend for the reprocessing cost is presented in Figure
Reprocessing cost trend.
The reprocessing costs show a decreasing trend since 1985 except in the MIT and De Roo study.
The decreasing trend could be explained by the technical and economic improvements of the reprocessing technology, which have turned it into a mature technology and consequently could have led to a cost decrease. This also will apply to the technology of the DGR, in a medium-long term, although this should not happen in the next years, due to the high level of uncertainties of estimates based on design studies, as stated in the OCDE study of 1993 [
Other nonquantifiable economic factors should be considered to carry out a comparison between both spent fuel strategies; open cycle with direct disposal and closed cycle with reprocessing of the spent fuel. As stated in the OCDE study on the DGR of 1993, the disposal of spent fuel or reprocessing waste is expected to be a highly controversial political issue in most countries, and the social and political issues will inevitably affect the costs [
There, reprocessing and recycling of the spent fuel seems to be the most sustainable strategy mainly because of the reduction of total volume of final waste to dispose.
The nonquantifiable economic factors are the intangibles assets. The most noteworthy intangible assets are Reprocessing and recycling strategies save up to 25% uranium ore, as explained before, reducing the volume of nuclear waste to disposal by a factor of 5 as well as the thermal load. The relative radiotoxicity and the radioactive decay are considered to be intangibles assets, difficult to evaluate quantitatively yet offering an undisputed added value compared to the open cycle, from a public opinion viewpoint. The relative radio toxicity level is reduced by a factor of 10, as can be observed in Figure The separation of plutonium 239 from spent nuclear fuel in the reprocessing phase and its later recycling into MOX avoids the nuclear proliferation. The plutonium of the spent MOX fuel is less appropriate for use in nuclear weapons. The vitrified waste products, including the products obtained in the fission, are initially beta-gamma emitters, so the radioactive emission capacity is reduced in about some five-hundred years.
Radioactive decay. Source: adapted from Commissariat à l’énergie atomique 2013 [
An opinion survey carried out in seven countries in 2010 showed that almost 80% of the respondents would advise their governments to begin recycling used nuclear fuel immediately, by using existing industrial solutions [
It is also necessary to consider the current instability of the Spanish legal landscape as exemplified by the draft bill on tax measures related to environmental and sustainable energy, placing new taxes on the value of electric energy generation, the production of spent nuclear fuel and the radioactive waste resulting from nuclear energy generation as well as on the storage of spent nuclear fuel, and radioactive waste in centralized interim storage facility (ATC).
Article 22 from Chapter III of the Spanish Bill on the Storage of High Level Waste and Spent Fuel distinguishes between spent fuel, whose taxable base is per kilogram of heavy metal, and other highly active waste, whose taxable base is per cubic meters. Spent nuclear fuel is taxed per kilogram of heavy metal stored, at a rate of 70€/kg HM. Radioactive waste will be taxed per cubic meter, at a rate of 30,000€/m3.
It should be noted that this distinction carries with it consequences for reprocessed Spanish used fuel: the tax applied to spent fuel will no longer be applied to the content of heavy metal in the stored fuel elements but rather, only to the 5th part: vitrified and compacted waste returned to Spain after being reprocessed-recycled, changing the taxable base and the applicable rate.
Also noteworthy is the fact that in the 6th GRWP, calculations for DGR cost have not been explicitly included as such. The base has been calculated up until 2070; however, many management and long-term costs for the construction of a DGR or for solutions such as transmutation have not been included while the implied costs for the DGR may have been underestimated, as can be deduced from the increase between the calculations of ENRESA between 1999 and 2006: the 6th GRWP acknowledged a 40% costs increase between the 2006 estimates and the last calculations made in 1999 for the interim storage [
When it comes to comparing global costs for the management of spent nuclear fuel, the studies analyzed in this report face considerable uncertainties due to two principle reasons: first, because this is a very long-term management issue, these theoretical and forward-looking studies must make several estimations based on the costs of certain processes that have yet to be fully developed and implemented, for a period of time in which costs could potentially change and be influenced by a variety of factors that are not currently known or quantifiable. Also, there are uncertainties related to these same characteristics of the potential management options: the overall cost of the open cycle as it is impacted by the estimated cost of certain solutions that have yet to be implemented on an industrial level, and in the closed cycle, as it deals with costs of commercial services that depend upon offers and are subjected to the policies of the service-providing company. As a consequence, the results of these comparative studies depend considerably upon the hypothesis which is chosen by the research team, explaining in great part why there are conflicting findings. However, we have determined that, in all of the studies, two factors decisively impact the overall cost of each option: the estimated cost of the deep geological repositories (DGR) in the open cycle and the reprocessing costs in the closed cycle. According to the information accumulated from all of the reports consulted, it was determined that while the costs associated with the DGR in the open cycle increase with time, due to the increasing uncertainties associated with the technology and its associated costs, the economic data related to the use of reprocessing decreases, precisely for the opposite reason, as this is a mature technology being consistently improved, with experience and R&D resulting in the lower prices. Controlled future back-end costs will significant decrease back-end’s financial uncertainties going along recycling option thanks to mature industry. On the contrary, there is an important financial risk for used fuel disposal for which encapsulation is still under development and economic evaluation is usually revised upwards. Limitation of financial risk is related to final disposal along with recycling thanks to the volume, heat load, and radiotoxicity reduction and final waste conditioning in standard canisters.
This conclusion leads us to recall the advantage offered by the reprocessing-recycling option in the decrease of uncertainties, as it deals with known, stable and applied costs in a horizon that is closer to the production of used fuel.
It is also important to recall that the choice between direct deposal and recycling of spent nuclear fuel does not depend solely on a vision of industrial management responding to the criterion of economic profitability but also depends on a global energy policy. Thus, the decision must take into account logic behind environmental and social sustainability. Here, the intangible assets of reprocessing and subsequent recycling offer a more sustainable solution that greatly reduces the volume and toxicity of the final waste product that is to be stored—the legacy that is to be inherited by our future generations, and principal preoccupation of our fellow citizens.